Reduce the sync window from 20 items to 5 (partial fix #2149029)
* This change trades off network time / overhead with time keeping
ContactsProvider2 busy
* The net effect will probably be to reduce some UI slowdowns while
syncing Exchange contacts, while increasing the time it takes to
sync those contacts
Change-Id: I56e2358698aa4c901cda4559f7a8f9117681f627